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    Re: Global oceanic tides, was: Navigating Around Hills and Dips in the Ocean
    From: Trevor Kenchington
    Date: 2003 Aug 16, 22:16 -0300

    Fred Hebard wrote:
    > Trevor,
    > Tidal levels may be calculated, but have satisfactory descriptions of
    > currents been acheived?  I believe George Huxtable was including both
    > in his description.
    Good point, Fred.
    I don't know whether anyone has attempted to model tidal streams in the
    ocean. (They are usually tiny: The tidal heights are not great, while
    the volume of water needed to make the difference between high water and
    low can often move as a current 4,000 metres deep. That means that the
    rate of drift is very small.)
    Where coastal tidal streams are concerned: Yes, they have been
    satisfactorily modelled, in some cases. I'm a tidal enthusiast, not a
    tidal expert, and I don't pretend to be up to date with the scientific
    literature. However, I'll offer the example of the Canadian Hydrographic
    Service's tidal atlases. Those are based entirely on the output from
    computer models (at least the Bay of Fundy/Gulf of Maine atlas and the
    Strait of Georgia atlas both are -- I think the St.Lawrence River one is
    too but I am not fully certain). [CHS publishes only the three tidal
    atlases.] Then again, I am not sure to what extent those models use
    empirical observations of the tide as input data (rather than just
    seabed morphology and astronomic tide-generating forces) so it might be
    argued that they do not truly represent observed tidal streams by
    calculating from theory alone.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus@iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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